1. Field of the Invention
The present invention relates to installation of a wear-resistant chip on a mechanical part such as a valve bridge, valve lifter, or the like part of a multi-valve engine which is required to have a good wear resistance at a portion for contact with another mechanical part.
2. Description of the Prior Art
A valve bridge for use in an engine of the type having four valves per each cylinder is shown in FIG. 7 as an example of a mechanical part of the above described kind.
The valve bridge "A" is a mechanical part which is pushed by an end of a rocker arm "B" for operating two valves "C" simultaneously. The valve bridge "A" and the rocker arm "B" are strongly rubbed against each other during the operation, of the engine and therefore liable to be worn out at the rubbed portions. In order to increase the wear resistance of a portion of the valve bridge "A", i.e., the portion for contact with the rocker arm "B", the valve bridge "A", as for example described in Japanese Utility Model Provisional Publication Nos. 63-202705 and 2-114702, has at a portion for contact with the rocker arm "B" a recess "D" in which a wear-resistant member "E" made of ceramics, or the like is installed.
In the structure disclosed by Japanese Utility Model Provisional Publication No. 63-202705, the wear-resistant member "E" is simply fitted in the recess "D". On the other hand, in the structure disclosed by Japanese Utility Model Provisional Publication No. 2-114702, a metallic intermediate member is interposed between the recess "D" and the wear-resistant member "E" and plastically deformed with a jig or tool such that the wear-resistant member "E" is fixedly held in the recess "D" by the effect of the plastically deformed intermediate, member.
A problem with the structure disclosed by Japanese Utility Model Provisional Publication No. 63-202705 is that the wear-resistant member "E" has a possibility of being dropped off from the recess "D" at the time of installation of the valve bridge "A" on the engine or at the time of maintenance of same, thus considerably deteriorating the working efficiency. When the recess "D" and the wear-resistant member "E" are more tightly fitted so that such dropping off does not occur, there is a necessity of grinding the peripheral portion of the wear-resistant member "E" to increase the dimensional accuracy, thus resulting in an increased manufacturing cost.
The structure disclosed by the Japanese Utility Model Provisional Publication No. 2-114702 is free from the above described problem since the wear-resistant member "E" is fixedly held by the intermediate member. However, this structure results in a high cost since a particular tool and a particular process for bending the intermediate member are necessitated and further since bending of the intermediate member may possibly cause a chipping of the wear-resistant member "E" particularly when the wear-resistant member "E" is made of ceramics or the like brittle material and may possibly cause a residual stress which deteriorates the durability.